Scientists Find A Water-Rich Planet Outside Our Solar System

Alex Knapp
,
Forbes Staff
I write about the future of science, technology, and culture.

(Credit: NAOJ)

Japanese scientists have determined that a planet outside our solar system that most likely has a water-rich atmosphere. The planet, Gliese 1214b, is only 40 light years from Earth.

Discovered in 2009, Gliese 1214b is what's known as a "super-Earth" - bigger than Earth but smaller than a gas giant. In this case, it's about 2.7 times bigger than Earth.

Based on the original research after the discovery of Gliese 1214b, scientists were able to determine its mass, radius and density. But what still wasn't known was the composition of the planet. Given the data, there were two major possibilities: first, that the planet was rocky, with a hydrogen atmosphere. The alternative is that the planet might be an "ocean world" comprised mostly of water.

To figure out which was the case, a team of Japanese researchers used the Subaru Telescope. They geared their observations with the telescope to determine whether Gliese 1214b showed signs of "Rayleigh scattering." Rayleigh scattering refers to how light is scattered by particles that are smaller than the wavelength of light traveling through it. For example, our sky on Earth is blue because of the way the atmosphere causes Rayleigh scattering of sunlight.

If Gliese 1214b had a hydrogen atmosphere, then astronomers would expect very strong Rayleigh scattering to occur. However, the results didn't show that. This indicates that the most likely possibility, given previous research on the planet, is that the planet's atmosophere is rich in water vapor. (There's also a chance that it's a hydrogen atmosphere with lots of clouds, but that's less likely.)

The researchers intend to do more observations of the planet to more definitively rule out the possibility of a hydrogen atmosophere for Gliese 1214b. However, given the facts to date, a water-rich planet is still the best possibility. Once that's confirmed, astronomers will have a better idea about how super-Earths, which are fairly common throughout our galaxy, form in the first place.

And that might also help astronomers determine why there isn't a super-Earth in our own Solar System.